A5081575949- Magnetism in coordination complexes
- Crystallization and Solubility Studies
- X-ray Diffraction in Crystallography
- Lanthanide and Transition Metal Complexes
- Magnetic properties of thin films
- Electron Spin Resonance Studies
- Graphene research and applications
- Organic and Molecular Conductors Research
- Diamond and Carbon-based Materials Research
- Rare-earth and actinide compounds
- Advanced NMR Techniques and Applications
- Semiconductor materials and interfaces
- Iron-based superconductors research
- Microstructure and mechanical properties
- Quantum Computing Algorithms and Architecture
- Glass properties and applications
- Photonic and Optical Devices
- Quantum Information and Cryptography
- Material Dynamics and Properties
- Quantum optics and atomic interactions
- Advancements in Semiconductor Devices and Circuit Design
- Advanced Memory and Neural Computing
- Crystallography and Radiation Phenomena
- Inorganic Chemistry and Materials
- Graphene and Nanomaterials Applications
European Synchrotron Radiation Facility
2017-2024
Université de Toulouse
2013-2020
Laboratoire de Chimie de Coordination
2013-2020
Institut Charles Gerhardt Montpellier
2014-2017
Université de Montpellier
2013-2017
Centre National de la Recherche Scientifique
2013-2017
Institut National Polytechnique de Toulouse
2014-2017
Université Toulouse III - Paul Sabatier
2013-2017
Institut de Chimie
2015
Laboratoire Charles Coulomb
2013-2014
The ultimate surface exposure provided by graphene monolayer makes it the ideal sensor platform but also exposes its intrinsic properties to any environmental perturbations. In this work, we demonstrate that charge carrier density of exfoliated on a SiO2/Si substrate can be finely and reversibly tuned between hole electron doping with visible photons. This photo-induced happens under moderate laser power conditions is significantly affected cleaning method. particular, requires hydrophilic...
Molecular spin crossover complexes are promising candidates for mechanical actuation purposes. The relationships between their crystal structure and properties remain, however, not well understood. In this study, combining high pressure synchrotron X-ray diffraction, nuclear inelastic scattering, micromechanical measurements, we assessed the effective macroscopic bulk modulus (B = 11.5 ± 1.5 GPa), Young's (Y 10.9 1.0 Poisson's ratio (ν 0.34 0.04) of complex [FeII(HB(tz)3)2] (tz...
Abstract The lattice dynamical aspects of the spin crossover phenomenon in molecular solids—displaying intricate couplings between electronic state molecules and properties—are reviewed. Emphasis is on experimental theoretical approaches giving access to vibrational spectra key properties, such as heat capacity, entropy enthalpy, rigidity, elastic constants, interactions. Recent results relation surface finite size effects well with ultrafast out‐of‐equilibrium phenomena are also covered.
In recent years, study of nano-objects with first-order phase transitions has raised new interesting questions. Indeed, the stability and transformation kinetics are highly dependent on object size. case spin crossover phenomenon size effects may lead to a loss hysteresis (bistability) properties, shift transition temperature or occurrence an incomplete also reappearance upon extreme reduction (∼1–4 nm). Research in this area is growing, but mechanisms at nanoscale particular dependence...
We used nuclear inelastic scattering (NIS) to investigate the lattice dynamics in [Fe(pyrazine)(Ni(CN)${}_{4})]$ spin crossover nanoparticles. The vibrational density of states iron was extracted from NIS data, which allowed determine characteristic thermodynamical and dynamical parameters as well their spin-state dependence. optical part spectra compares with Raman data reflecting expansion/contraction coordination octahedron during transition. From acoustic part, we sound velocity low-spin...
The spin transition behavior in nanoparticles of molecular crossover (SCO) materials is investigated theoretically using a two-variable microscopic Ising-like model solved by Monte Carlo simulations. extensive nature the energy, and therefore whole thermodynamics affected increasing role surface energetic parameters. As consequence pressure inside nanoparticle different from external bath. difference energies between low (LS) high (HS) states origin modification SCO properties at finite...
Abstract When a liquid is cooled to produce glass its dynamics, dominated by the structural relaxation, become very slow, and at glass-transition temperature T g characteristic relaxation time about 100 s. At slightly elevated temperatures (~1.2 ) however, second process known as Johari-Goldstein β JG , decouples from one remains much faster than it down . While that -process strongly coupled dedicated role in under debate. Here we use an experimental technique permits us investigate spatial...
Understanding the glass transition requires getting picture of dynamical processes that intervene in it. Glass-forming liquids show a characteristic decoupling relaxation when they are cooled down towards glassy state. The faster (βJG) process is still under scrutiny, and its full explanation necessitates information at microscopic scale. To this aim, nuclear γ-resonance time-domain interferometry (TDI) has been utilized to investigate 5-methyl-2-hexanol, hydrogen-bonded liquid with...
An unexpected upshift of the spin transition temperature by ca. 3 K is observed in thermally evaporated films [FeII(HB(tz)3)2] (tz = 1,2,4-triazol-1-yl) complex when reducing film thickness from 200 to 45 nm. Fitting experimental data continuum mechanics and thermodynamical models allows us propose an explanation based on anisotropy transformation strain leading ∼5 mJ/m2 higher 00l surface energy high-spin phase.
A series of spin-crossover (SCO) coordination nanoparticles (ca. 60 nm) with the general formulae [Fe(Htrz)1+y-x(trz)2-y(NH2trz)x](BF4)y·nH2O (x = 0, 0.1, 0.2 and 0.3) were synthesized in concentrated solutions without using any surfactant or polymer. The nanoparticle powders investigated by transmission electron microscopy, powder X-ray diffraction, magnetometry, calorimetry, Raman/IR spectroscopies, elemental analysis 57Fe Mössbauer spectrometry. Remarkably, latter revealed a large...
Size reduction leads to drastic changes in thermodynamic properties spin‐crossover (SCO) nano‐objects comparison with bulk materials. In particular, an important modification of the phase stability has been observed, reflected by a shift transition temperature. These are mostly attributed increasing role surface at nanoscale, especially elastic properties, which play key SCO phenomena. this work, we propose continuum mechanics approach explore possibility tune controlling interfacial energy...
The influence of surface/interface on the lattice dynamics spin crossover nanoparticles has been investigated by a spring-ball model solved Monte Carlo methods. bond cohesion energy extracted from M\"ossbauer spectroscopy measurements performed compound ${\mathrm{Ni}}_{3}[\mathrm{Fe}{(\mathrm{CN})}_{6}]$. We show that coupling between bulk and surface vibrational properties, which drastically affects mechanical properties whole particle below characteristic size, major impact phase stability...
We analyse in detail the role of surface relaxations on spin transition phenomenon through an Ising-like model solved inhomogeneous mean field approach. show relaxation tends to decrease energy cost missing bonds. Cooperative phenomena are also affected, leading asymmetric hysteresis loop. The underlying mechanisms investigated by calculating thermodynamics excess quantities. Far from transition, contribution internal energy, entropy and free is negligible, but their becomes substantial...
We report the investigation of size evolution lattice dynamics in spin crossover coordination nanoparticles $\mathrm{[}\mathrm{Fe}(\mathrm{pyrazine})(\mathrm{Ni}{(\mathrm{CN})}_{4})]$ through nuclear inelastic scattering (NIS) measurements. Vibrational properties these bistable molecular materials are paramount importance and NIS permits access to partial vibrational density states both [high (HS) low (LS)] from which thermodynamical mechanical can be extracted. show that reduction leads...
The magnetic and structural properties of the recently discovered pnictogen/chalcogen-free superconductor LaFeSiH have been investigated by $^{57}\mathrm{Fe}$ synchrotron M\"ossbauer source spectroscopy, X-ray neutron powder diffraction, $^{29}\mathrm{Si}$ nuclear resonance spectroscopy. In contrast with earlier work suggesting presence an orthorhombic ground state as in underdoped Fe-based pnictides, our results unambiguously establish that is fact similar to strongly overdoped pnictides:...
In the first part of this work, an experimental study lattice dynamics spin crossover nanoparticles was performed using nuclear inelastic scattering (NIS). A size dependence low energy phonon modes appears under 10 nm, but its origin is not well understood. paper, we investigate confinement effects in framework molecular simulations by modeling three-dimensional considering a cubic with octahedral pattern. The vibrational density states computed and compared to experiment. allow one...
We report on the elastic properties of Ni/[Fe(CN) 6 ] Prussian‐blue‐analogue nanoparticles investigated by high‐pressure synchrotron X‐ray diffraction and nuclear inelastic scattering. For 3 nm 115 particles, we have obtained bulk moduli (30.3 ± 3.8) GPa (24.5 3.2) GPa, with Debye sound velocities (2496 46) m s –1 (2407 38) , respectively. Combining these results, Poisson's ratio, Young's modulus, shear transversal/longitudinal been calculated for each particle size. All physical quantities...
Spin crossover is unambiguously demonstrated by magnetic and electrical measurements in ordered self-assemblies of ultra-small platinum nanoparticles with coordination polymers.
Spin-crossover nanomaterials have been actively studied in the past decade for their potential technological applications sensing, actuating, and information processing devices. Unfortunately, an increasing number of metallic centers become inactive at reduced sizes, presumably due to surface effects, limiting switching ability thus scope applications. Here we report on investigation "frozen" nanoparticles (2–80 nm size) spin-crossover compound Fe(pyrazine)[Ni(CN)4]. Magnetic measurements...
Effects of A-site and M-site substitutions on the structural properties perovskite dimethylammonium iron formate.
We determined the lattice dynamics of metastable, surface-stabilized $\ensuremath{\alpha}$-phase ${\mathrm{FeSi}}_{2}$ nanoislands epitaxially grown on Si(111) surface with average heights and widths ranging from 1.5 to 20 nm 18 72 nm, respectively. The crystallographic orientation, morphology, local crystal structure were investigated by reflection high-energy electron diffraction, atomic force microscopy, x-ray absorption spectroscopy. Fe-partial phonon density states (PDOS), obtained...